[Gllug] Getting an IP address at a public WiFi point

[Mark Williams]

John Winters wrote:
> I've just returned from holiday and noticed a recurring problem when
> trying to use public (and other) WiFi access points.
> 
> At home, my laptops work fine from my WiFi point (WPA-PSK) and also from
> various other ones at other people's houses.
> 
> At the house where I was staying in France there was a dual access point
> provided by SFR.  It had a secured i/f for the householder, and a public
> i/f for use by other SFR customers who happened to be in range (not
> likely in the depths of rural France).  I could connect to the latter,
> but even once I'd worked out the correct authentication details (the
> ones printed on the bottom of the router were wrong) I couldn't connect
> to the full-fat secure point.  I got past authentication OK, but then my
>  laptop would sit there sending DHCP requests and getting no response.
> After 1 minute it would time out and allocate itself one of those DIY IP
> addresses.  (As an aside - what is the point of this behaviour?  I've
> never come across an instance where it provides you with any kind of
> connectivity.  It just makes life more difficult.)
> 
> Back to the main point - I also got much the same performance trying to
> use public access points - e.g. on the Britanny Ferries boat on the way
> home.  I could get past authentication, but then DHCP requests were all
> ignored.  I tried both Network Manager and Wicd, and various different
> DHCP clients under Wicd (Network Manager doesn't offer a choice).  Of
> course the suppliers just say, "We support only Windows" so there's no
> help there.  (SFR went even further - their website says, "Windows only
> - no Macs, no Linux")
> 
> How do Windows boxes get IP addresses from such access points?  Does
> anyone know any special tricks you can use to get connectivity?
> 
> TIA,
> John

I had a similar experience on a cruise ship - however they had a guy who 
knew their system, but not Linux, so we pooled skills.

The problems there was netmasks - Windows is broken and ignores the 
netmask, so some systems send an incorrect version. This means you get 
past network auth, but then DHCP sends you duff stuff.

I used a little script to login which simply reset it, thus in effect 
emulating M$ misbehaviour, and it worked.

The perpetrator, I forget the name, was a London-based ISP.

Mark

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